Still, shares of Depomed traded above the revised offer price Tuesday, indicating investors may not think the bid will be enough to secure a deal. Shares of Depomed were up 2.3% to $33.50 midday, while Horizon shares fell 0.3% to $37.20.

The offer of $33 a share is up from Horizon’s previous bid of $29.25 a share, which Depomed rejected in late May. The new offer represents a premium of 60% based on Depomed’s closing price on July 6, the day before the initial offer was made. The increased offer is contingent on Depomed agreeing to work with Horizon

Depomed acknowledged receipt of the bid Tuesday and said it would review it. Its board had earlier said the proposal was “not in the best interest” of the company, given that it is in a period of significant growth and is expected to benefit from its recent acquisition of the U.S. rights to painkiller Nucynta from Janssen Pharmaceuticals Inc., a unit of Johnson & Johnson.

Earlier this month, Depomed adopted a poison-pill plan that would be triggered by a person or group acquiring a more than 10% stake in the company, in an effort to stave off a takeover.

Under the terms, shareholders of Depomed, which makes pain treatments, would own about 25% of the combined company. Horizon, which focuses on treatments for orphan diseases, said it went public with its offer because Depomed executives refused to engage in talks with Horizon.

Horizon Chief Executive Officer Timothy Walbert said in a statement that buying Depomed would generate “significant revenue and operating synergies, as well as considerable tax savings.” Depomed paid 38% of its profits in taxes last year, according to regulatory filings. Ireland has a 12.5% corporate tax rate.